<?php
// <!-- 公共的返回header的子程序 -->
function sendheader($last_modified, $p_type, $content_length = 0) {
	// 设置客户端缓存有效时间
	header("Expires: " . gmdate("D, d M Y H:i:s", time() + 15360000) . "GMT");
	header("Cache-Control: max-age=315360000");
	header("Pragma: ");
	// 设置最后修改时间
	header("Last-Modified: " . $last_modified);
	// 设置文件类型信息
	header($p_type);
	header("Content-Length: " . $content_length);
}

define('ABSPATH', dirname(__FILE__) . '/');

$cache = true;
$cachedir = 'cache/'; //存放gz文件的目录，确保可写

if (empty($_SERVER['QUERY_STRING'])) exit();

$gzip = strstr($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip');
if (empty($gzip)) $cache = false;

$key = array_shift(explode('?', $_SERVER['QUERY_STRING']));
$key = str_replace('../', '', $key);

$filename = ABSPATH . $key;

$symbol = '_';

$rel_path = str_replace(ABSPATH, '', dirname($filename));
$namespace = str_replace('/', $symbol, $rel_path);

$cache_filename = ABSPATH . $cachedir . $namespace . $symbol . basename($filename) . '.gz'; //生成gz文件路径

$ext = array_pop(explode('.', $filename)); //根据后缀判断文件类型信息

$type = "Content-type: text/html"; //默认的文件类型
switch ($ext) {
	case 'css':
		$type = "Content-type: text/css";
		break;
	case 'js':
		$type = "Content-type: text/javascript";
		break;
	case 'gif':
		$cache = false;
		$type = "Content-type: image/gif";
		break;
	case 'jpg':
		$cache = false;
		$type = "Content-type: image/jpeg";
		break;
	case 'png':
		$cache = false;
		$type = "Content-type: image/png";
		break;
	default:
		exit();
}

if ($cache) {
	if (file_exists($cache_filename)) { // 假如存在gz文件
		$mtime = filemtime($cache_filename);
		$gmt_mtime = gmdate('D, d M Y H:i:s', $mtime) . ' GMT';

		if ((isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) &&
					array_shift(explode(';', $_SERVER['HTTP_IF_MODIFIED_SINCE'])) == $gmt_mtime)
				) {
			// 与浏览器cache中的文件修改日期一致，返回304
			header ("HTTP/1.1 304 Not Modified");
			// 发送客户端header
			header("Content-Encoding :gzip");
			sendheader($gmt_mtime, $type);
		} else {
			// 读取gz文件输出
			$content = file_get_contents($cache_filename);
			// 发送客户端header
			sendheader($gmt_mtime, $type, strlen($content));
			header("Content-Encoding: gzip");
			// 发送数据
			echo $content;
		}
	} else if (file_exists($filename)) { // 没有对应的gz文件
		$mtime = mktime();
		$gmt_mtime = gmdate('D, d M Y H:i:s', $mtime) . ' GMT';
		// 读取文件
		$content = file_get_contents($filename);
		// 去掉空白的部分
		// $content = ltrim($content);
		// 压缩文件内容
		$content = gzencode($content, 9, $gzip ? FORCE_GZIP : FORCE_DEFLATE);
		// 发送客户端header
		sendheader($gmt_mtime, $type, strlen($content));
		header("Content-Encoding: gzip");
		// 发送数据
		echo $content;
		// 写入文件
		file_put_contents($cache_filename, $content);
	} else {
		header("HTTP/1.0 404 Not Found");
	}
} else { // 处理不使用Gzip模式下的输出。原理基本同上
	if (file_exists($filename)) {
		$mtime = filemtime($filename);
		$gmt_mtime = gmdate('D, d M Y H:i:s', $mtime) . ' GMT';

		if ((isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) &&
					array_shift(explode(';', $_SERVER['HTTP_IF_MODIFIED_SINCE'])) == $gmt_mtime)
				) {
			// 与浏览器cache中的文件修改日期一致，返回304
			header ("HTTP/1.1 304 Not Modified");
			// 发送客户端header
			sendheader($gmt_mtime, $type, strlen($content));
			header("Content-Encoding :gzip");
		} else {
			// 读取文件输出
			$content = file_get_contents($filename);
			// 发送客户端header
			sendheader($gmt_mtime, $type, strlen($content));
			// 发送数据
			echo $content;
		}
	} else {
		header("HTTP/1.0 404 Not Found");
	}
}

?>